A new concert hall in Dallas, Tex., has the first acoustical design done with the aid of computer simulations that also dictated the shape of the performance space. Those dictates, in turn, posed structural engineering constraints involving several massive column transfers. The building itself is a rectangular performance space with four tiers, set into a lower circular structure that incorporates the lobby, a balcony, a garden and a restaurant. The point where the two shapes meet are dealt with by an innovative ring beam that spans three sides of the rectangle and ties the two shapes together, structurally and esthetically. The 45 ft glass curtain walls of the lobby were another structural engineering challenge. To control deflection of long span roof girders, webs were fabricated with several inches of camber, and preloaded in the field. After this operation, the roof was placed.